Hi

You don't need to pay tax, GCC has one tax law, you need to get a import paper and taxed paid slip from Dubai customs or the port where the car was originally came into UAE.

You can buy 15 days insurance at the Dubai registration dept when you make the export plate, you can drive the car in Doha on it for few days, then get it insured here and take it to madina khalifa for registration.

it is quite simple

Good Luck